The present invention relates to a variable displacement piston pump/motor using optimal hydraulic pressure and acting as a drive source for hydropneumatic presses, hydraulic motors, or the like.
Japanese laid-open patent publication number 4-228924 and others disclose variable displacement piston/pump motors in which an input or output shaft angle (theta) is manipulated to control the discharge volume or the rotation output of a pump. Also, Japanese laid-open patent publication number 10-18962 discloses a variable displacement swash-plate hydraulic pump. In this technology, a manual traction lever is used to tilt the swash plate from a neutral, perpendicular position relative to the drive shaft to either the positive or the negative direction, thus controlling an axial piston, which makes a reciprocating motion inside a cylinder block.
In the former device, the angle (theta) of the shaft must be changed in order to change the discharge volume of the pump or the rotation speed of the pump motor. Thus, when a drive shaft serving as a rotating load on the shaft is connected directly, the housing is fixed, making it necessary for the shaft angle to be fixed. In other words, the output capacity and the rotation speed cannot be changed. If the shaft position were to be fixed and the housing were to be tilted, flexible, tightly sealed tubing must be used since the intake opening and the discharge opening are positioned axially. As a result, implementing this type of device becomes complex.
In the latter hydraulic pump, a drive shaft is passed through the swash plate, and this swash plate is tilted to control the discharge volume. Thus, a large tilting angle cannot be used, and even if a large angle were to be used, the size of the hydraulic pump would necessarily increase, making it unsuitable for compact, light-weight designs.
The object of the present invention is to provide a variable displacement piston pump/motor that is compact, that has a simple structure, and that can operate in a stable manner.
Another object of the present invention is to provide a variable displacement piston pump/motor that can be tilted with a small traction force.
Yet another object of the present invention is to provide a variable displacement piston pump/motor that allows a desired tilting angle to be reliably approached using a small drive force.
Yet another object of the present invention is to provide a variable displacement piston pump/motor that can easily be used in CNC (Computer Numerical Control).
In the present invention, it would be desirable for a shaft support cylinder to have a spherical outer perimeter surface and to have a spherical surface contact between this surface and one end of a housing.
In a variable displacement piston pump/motor according to the present invention, the variable displacement piston pump/motor is disposed in a cylindrical housing with one end covered by a side cover. The side cover includes: input/output shafts maintaining a fixed relationship; a cylinder block facing the shafts, another end of the cylinder block disposed on the side cover via a valve plate; a drive pin interposed between and connecting the cylinder block and the shafts; and a plurality of concentric piston devices disposed around the drive pin, providing rotation output or hydraulic discharge force, and including spherical heads pivotably supported by an end surface of the shaft. The input/output shafts are pivotably supported by another end of the housing via a shaft support cylinder formed with a spherical outer surface. The housing can be tilted freely in one direction, pivoting around hydraulic intake/discharge path-forming tubes fixed on lines connecting centers of the spherical heads of the pistons.
In the present invention, a traction lever attachment mechanism is disposed at an axis center section of an outer side surface of the side cover. Pulling the traction lever attachment mechanism in one direction applies a tilting angle to the housing.
Traction lever can be formed from a threaded shaft meshed with a pivot pin rotatably disposed on a plate fixed to the side cover. The traction lever is controlled by externally applied forward or reverse rotation.
In the present invention, a base of the threaded shaft can be rotatably supported by a boss that is pivotably supported by a pivot pin.
A servo motor can be used to apply rotation force to the threaded shaft.
The above, and other objects, features and advantages of the present invention will become apparent from the following description read in conjunction with the accompanying drawings, in which like reference numerals designate the same elements.